Questions and Answers About EMF Electric and Magnetic Fields Associated with the Use of Electrical Power.
January 1995.

Human Health Studies

Q. Do electrical workers have higher risks of cancer?

A. Several studies have reported increased cancer risks for jobs involving work around electrical equipment. To date, it is not clear whether these risks are caused by EMFs or by other factors. A report published in 1982 by Dr. Samuel Milham was one of the first to suggest that electrical workers have a higher risk of leukemia than do workers in other occupations. The Milham study was based on death certificates from Washington state and included workers in 10 occupations assumed to have elevated exposure to EMFs. A subsequent study by Milham, published in 1990, reported elevated levels of leukemia and lymphoma among workers in aluminum smelters, which use exceptionally high levels of electrical power.

About 50 studies have now reported statistically significant increased risks for several types of cancer

in occupational groups presumed to have elevated exposure to EMFs. Relative risk levels in these studies are mostly less than 2, and the possible influence of other factors such as chemicals has not been ruled out. At least 30 other studies did not find any significant cancer risks in electrical workers. Most of the earlier occupational studies did not include actual measurements of EMF exposure on the job. Instead, they used "electrical" job titles as indicators of assumed elevated exposure to EMFs. Recent studies, however, have included extensive EMF exposure assessments.

A report published in 1992 by Dr. Joseph Bowman and colleagues provided some information about actual EMF exposures of various electrical workers. As shown in the table below, electrical workers in Los Angeles and Seattle did have higher EMF exposures than nonelectrical workers.

Please note: you must be using NCSA Mosaic 2b3 or later or Netscape 1.1 or later to view the table below.

In a further analysis published in July 1994, Dr. Stephanie London, Bowman, and others found a weakly positive trend for increased leukemia risk in relation to exposure to magnetic fields among electrical workers in Los Angeles County. These results were consistent with findings from studies based on job title alone that electrical workers may be at slightly increased risk of leukemia.

A 1993 study (Sahl et al.) of 36,000 electrical workers at a large utility in California found some elevated risks for leukemia, but they were not statistically significant. The study found no consistent evidence of an association between measured magnetic fields and cancer. A 1992 study of Swedish workers (Floderus et al.) found an association between average EMF exposure and chronic lymphocytic leukemia but not acute myeloid leukemia. There was some evidence of increasing risk with increasing exposure. The Floderus study also reported an increase in brain tumors among younger men whose work involved relatively high magnetic field exposure.

"AVERAGES"
There are two common ways of describing a middle value in a sample of measurements:

Mean = The sum of all measurements in a sample divided by the number of measurements.
Median = The middle measurement in a sample arranged in order of size. There are as many measurements larger than the median as there are smaller. The median is useful for data with some very high or very low measurements.

There were inconsistencies in results among the three utilities and no clear indication of a dose-response trend. The authors concluded, therefore, that their results did not provide definitive evidence that magnetic fields were the cause of the elevated risks found in leukemia and brain cancer. However, they observed as "noteworthy" the fact that despite the enormous number of analyses done, the only two types of cancer for which a significant association with EMF was found (leukemia and brain cancer) were among the three for which an association had been hypothesized, based on previous studies.

In another major study involving more than 138,000 utility workers (Savitz et al. 1995), the authors concluded that the results "do not support an association between occupational magnetic field exposure and leukemia, but do suggest a link to brain cancer."